Inductors can be formed or installed on integrated circuit (IC) chips for various applications. Examples include inductors in series with power rails to filter current “spikes,” e.g., from rapid switching of loads, and “LC” filters comprising various interconnects of inductors and capacitors.
One known IC chip inductor is the three-dimensional or “3D” inductor, such as the FIG. 1 example related art 3D inductor 100. The related art 3D inductor 100 is substantially embedded in and supported by a substrate, which is removed from FIG. 1 for purposes of visibility. Referring to FIG. 1, the example related art 3D inductor 100 is a rectangular coil or spiral, having a “winding axis” WX, and formed of a succession of rectangular turns (visible in FIG. 1, but not separately labeled). The device is termed “3D” because the rectangular turns are formed, in part by vias (visible, with one labeled 102), having a height normal to the substrate.
The related art 3D inductor 100 can have improved performance compared to other inductor designs, such as the known, conventional spiral two-dimensional planar (“2D”) inductor (not shown in FIG. 1). However, one shortcomings of the related art 3D inductor 100 includes monopolization of chip real estate, namely, each instance occupies its own volume and chip area. Another shortcoming can be constraints regarding spacing and relative orientation between adjacent instances of such 3D inductor devices. Such constraints may result from by requirements for minimizing cross-coupling.
FIG. 2 shows one example stacked two-dimensional (2D) spiral inductor 200, according to a known conventional technique. Referring to FIG. 2, the stacked 2D spiral inductor 200 includes a first, or lower 2D spiral inductor 202, supported on, for example a substrate surface (not visible in FIG. 2). Overlaying the lower 2D spiral inductor 202 is a second, or upper, 2D spiral inductor 204. However, because of the respective magnetic fields of the first and second 2D spiral inductors 202 and 204, and their respective alignment, significant cross-coupling may occur. The cross-coupling may render the FIG. 2 arrangement not practical or not preferred for some applications.
FIGS. 3A and 3B show one related art configuration 300 of neighboring instances of the FIG. 1 3D inductors, is an illustrative example of such spacing and orientation constraints. Referring to related art FIG. 3A, a first 3D coil 304 is substantially embedded in and supported by the substrate 302. The first 3D coil is orientated to have a winding axis “MA.” A second 3D coil 306 is also substantially embedded in the substrate 302, at a position adjacent to the position of the first 3D coil 304. The second 3D coil is oriented with its second magnetic winding axis “MB” orthogonal, or reasonably orthogonal to the winding axis MA.
FIG. 3B is a top projection, from the projection plane 1-1 of FIG. 3A, of the related art configuration 200 of neighboring instances of the FIG. 1 3D inductors. Referring to FIG. 3B, it seen that the related art configuration 300 causes area “AA” to be occupied by the first 3D coil 302, while an area “AB” is occupied by the second 3D coil 306. Negligible overlap or sharing between area AA and area AB is provided.